Surface roughness and wettability of two lesser-used wood species from Borneo, Indonesia

Abstract

Wettability is one of the important indicators in order to determine bonding quality of wood. It is generally known that surface roughness of wood affects wood wettability. The aim of this research was to investigate surface roughness and wettability of two lesser-used wood species from Indonesian tropical rain forest namely Octomeles sumatrana and Duabanga moluccana. Surface roughness was measured by a portable surface roughness tester, while wettability by contact angle measurement based on sessile drop method. Phenol formaldehyde and distilled water were used as reference liquid. A drop of liquid (0.02 ml) was placed in plainsawn-, quartersawn-, and semi-quartersawn-surface boards of each species. By analysis of variance, there was significantly difference in surface roughness between the two woods species. Surface roughness was not significantly correlated with the equilibrium contact angle (θe). Furthermore, wood species, liquid types, and their interaction have a significant effect on the θe. The two lesser-used wood species have different characteristics in anatomical structure, extractive content, wood acidity, and surface roughness. These all characteristics contribute to the wettability. The greater contact angle indicated the difficulty of PF for wetting the wood.